USPTO Patents Application 10687850

(12) INTERNATIONAL APPLICATION PUBLISHED UNDER THE PATENT COOPERATION TREATY (PCT)

(19) World Intellectual Property Organization
International Bureau

(43) International Publication Date
11 October 2001 (11.10.2001)

PCT

(10) International Publication Number

WO 01/75433 A2

(51) International Patent Classification 7 : G01N 33/00 (81) Designated States (national): AE, AG, AL, AM, AT, AU,

(21) International Application Number: PCT/US0 1/09237

(22) International Filing Date: 22 March 2001 (22.03.2001)
(25) Filing Language: English

(26) Publication Language:

English

(30) Priority Data:

09/541,376

3 i March 2000 (3 1 .03 .2000) US

(71) Applicant: LIFESCAN, INC. [US/US']; 1000 Gibraltar
Drive, Milpitas, CA 95035 (US).

(72) Inventor: SHARTLE, Robert, Justice; 1264 Geneve
Court, Livermore, CA 94550 (US).

AZ, BA, BB, BG, BR, BY, BZ, CA, CH, CN, CR, CU, CZ,
DE, DK, DM, DZ, EE, ES, Fl, GB, GD, GE, GH, GM, HR,
HU, ID, IL, IN, IS, JP, KE, KG, KP, KR, KZ, LC, LK, LR,
LS, LT, LU, LV, MA, MD, MG, MK, MN, MW, MX, MZ,
NO, NZ, PL, PT, RO, RU, SD, SE, SG, SI, SK, SL, TJ, TM,
TR, TT, TZ, UA, UG, UZ, VN, YU, Z A, ZW.

(84) Designated States (regional): ARIPO patent (GH, GM,
KE, LS, MW, MZ, SD, SL, SZ, TZ, UG, ZW), Eurasian
patent (AM, AZ, BY, KG, KZ, MD, RU, TJ, TM), European
patent (AT, BE, CH, CY, DE, DK, ES, FI, FR, GB, GR, IE,
IT, LU, MC, NL, PT, SE, TR), OAPI patent (BF, BJ, CF,
CG, CI, CM, GA, GN, GW, ML, MR, NE, SN, TD, TG).

Published:

— without international search report and to be republished
upon receipt of that report

(74) Agents: JOHNSON, Philip, S. etal.; Johnson & Johnson,
One Johnson & Johnson Plaza, New Brunswick, NJ 08933
(US).

For two-letter codes and other abbreviations, refer to the "Guid-
ance Notes on Codes and Abbreviations" appearing at the begin-
ning of each regular issue of the PCT Gazette.

(54) Title: CAPILLARY FLOW CONTROL IN A FLUTDIC DIAGNOSTIC DEVICE

20A

(57) Abstract: A medical diagnostic device for measuring
an analyte concentration or property of a biological fluid
includes capillary flow channels to convey a sample of the
fluid from an inlet to a branching point, and then to a mea-
surement area and , alternatively, through a bypass channel
to an overflow region. A first stop junction stops fluid flow
after it enters the measurement area. The bypass channel
has a capillary dimension in at least one direction. A sec-
ond stop junction, in the bypass channel, has a boundary
region that has a dimension that is greater in thai direction
and forms an angle that points toward the branching poinL
With this construction, the second stop junction initially
prevents flow to the overflow region, but permits the flow
after the measurement area is filled. The device is partic-
ularly suited for measuring coagulation time of blood.

WO 01/75433 PCT/US01/09237

5

CAPILLARY FLOW CONTROL IN A
FLUIDIC DIAGNOSTIC DEVICE

Cross-reference to Prior Application

This application relates to pending U.S. Applications 09/333,765, filed June 15,
1999; and 09/354,995, filed July 1 6, 1999.

BACKGROUND OF THE INVENTION

10 1 . Field of the Invention

This invention relates to a medical diagnostic device that includes an element
for controlling fluid flow through the device; more particularly, to a device that
facilitates fluid flow through a stop junction.

15 2. Description of the Related Art

A variety of medical diagnostic procedures involve tests on biological fluids,
such as blood, urine, or 20 saliva, to determine an analyte concentration in the fluid.
The procedures measure a variety of physical parameters - mechanical, optical,
electrical, etc., - of the biological fluid.

20 Among the analytes of greatest interest is glucose,and dry phase reagent strips

incorporating enzyme-based compositions are used extensively in clinical laboratories,
physicians' offices, hospitals, and homes to test samples of biological "fluids for glucose
concentration. In fact, reagent strips have become an everyday necessity for many of
the nation's estimated 16 million people with diabetes. Since diabetes can cause

25 dangerous anomalies in blood chemistry, it can contribute to vision loss, kidney failure,
and other serious medical consequences. To minimize the risk of these consequences,
most people with diabetes must test themselves periodically, then adjust their glucose
concentration accordingly, for instance, through diet, exercise, and/or insulin injections.
Some patients must test their blood glucose concentration as often as four 1 0 times

30 or more daily.

One type of glucose measurement system operates electrochemically, detecting
the oxidation of blood glucose on a dry reagent strip. The reagent generally includes an
enzyme, such as glucose oxidase or glucose dehydrogenase, and a redox mediator,
such as ferrocene or fenicyanide. This type of measurement system is described in U.S.
35 Pat. 4,224,125, issued on September 23, 1980, to Nakamura et al.; and U.S. Pat.

SUBSTITUTE SHEET (RULE 26)

WO 01/75433 PCT/US01/09237

-2-

4,545,382, issued on October 8, 1985, to Higgins et al., incorporated herein by
reference

Hodges et al., WO 9718464 Al, published on May 22, 1997, discloses an
electrochemical device for measuring blood glucose that includes two metallized
5 polyethylene terephthalate (PET) layers sandwiching an adhesive-coated PET

intermediate layer. The metallized layers constitute first and second electrodes, and a
cutout in the adhesive-coated layer defines an electrochemical cell. The cell contains
the reagent that reacts with the glucose in a blood sample. The device is elongated, and
. the sample is introduced at an inlet on one of the long sides.

10 The electrochemical devices for measuring blood glucose that are described in

the patents cited above, as 5 well as other medical diagnostic devices used for
measuring analyte concentrations or characteristics of biological fluids, generally share
a need to transport the fluid from a sample inlet to one or more other sections of the
device. Typically, a sample flows through capillary channels between two spaced-apart

15 surfaces. A number of patents, discussed below, disclose medical diagnostic devices
and include descriptions of various methods to control the flow of the sample,

U.S. Patent 4,254,083, issued on March 3, 1981, to Columbus, discloses a
device that includes a sample inlet configured to facilitate movement of a drop of fluid
sample into the device, by causing a compound meniscus to form on the drop. (See also

20 U.S. Patent 5,997,817, issued on December 7, 1999 to Crismore et al.)

U.S. Patent 4,426,451, issued on January 17, 1984 to Columbus, discloses a
multi-zone fluidic device that has pressure-actuatable means for controlling the flow of
fluid between the zones. His device makes use of pressure balances on a liquid
meniscus at the interface 25 between a first zone and a second zone that has a different

25 cross section. When both the first and second zones are at atmospheric pressure, surface
tension creates a back pressure that stops the liquid meniscus from proceeding from the
first zone to the second. The configuration of this interface or "stop junction" is such
that the liquid flows into the second zone only upon application of an externally
generated pressure to the liquid in the first zone that is sufficient to push the meniscus

30 into the second zone.

U.S. Patent 4,868,129, issued on September 19, 1989 to Gibbons et al.,
discloses that the back pressure in a stop junction can be overcome by hydrostatic
pressure on the liquid in the first zone, for example by having a column of fluid in the
first zone.

SUBSTITUTE SHEET (RULE 26)

WO 01/75433

PCT/US01/09237

-3-

U.S. Patent 5,230,866, issued on July 27, 1993 to Shartle et aL, discloses a
fluidic device with multiple stop junctions in which the surface tension-induced back
pressure at the stop junction is augmented; for example, by trapping and compressing
gas in the second zone. The 15 compressed gas can then be vented before
5 applying additional hydrostatic pressure to the first zone to cause fluid to flow into the
second zone. By varying the back pressure of multiple stop junctions in parallel,
"rupture junctions" can be formed, having lower maximum 20 back pressure.

U.S. Patent 5,472,603, issued on December 5, 1995 to Schembri (see also U. S.
Patent 5,627,041), discloses using centrifugal force to overcome the back pressure in a

10 stop junction. When flow stops, the first zone is at atmospheric pressure plus a

centrifiigally generated pressure that is less than the pressure required to overcome the
back pressure. The second zone is at atmospheric pressure. To resume flow, additional
centrifugal pressure is applied to the first zone, overcoming the meniscus back pressure.
The second zone remains at atmospheric pressure.

15 U.S. Patent 6,01 1,307, issued on December 14, 1999, to Naka et at, published

on October 29, 1997, discloses 5 a device and method for analyzing a sample that
includes drawing the sample into the device by suction, then reacting the sample with a
reagent in an analytical section. Analysis is done by optical or electrochemical means.
In alternate embodiments, there are multiple to analytical sections and/or a bypass

20 channel. The flow among these sections is balanced without using stop junctions.

U.S. Patent 5,700,695, issued on December 23, 1997 to Yassinzadeh et al.,
discloses an apparatus for collecting and manipulating a biological fluid that uses a
"thermal pressure chamber" to provide the driving force for moving the sample through
the apparatus.

25 U.S. Patent 5,736,404, issued on April 7, 1998, to Yassinzadeh et al, discloses a

method for detemiining the coagulation time of a blood sample that involves causing an
end of the sample to oscillate within a passageway. The oscillating motion is caused by
alternately increasing and decreasing the pressure on the sample.

None of the references discussed above suggest a device in which flow channel

30 has a stop junction that is angular in the flow direction.

SUMMARY OF THE INVENTION
This invention provides a medical device for measuring an analyte

concentration or property of a biological fluid. This embodiment of the
35 device comprises

SUBSTITUTE SHEET (RULE 26)

WO 01/75433

PCT/US01/09237

-4-

a) a sample inlet for introducing a sample of the biological fluid
into the.device;

b) a first capillary channel for conveying the sample from the inlet to a
branching point;

5 c) a capillary connecting channel for conveying a first part of the

sample from the branching point through a measurement area, in which is
measured a physical parameter of the sample that is related to the analyte
concentration or property of the .fluid, and to a first stop junction;

d) a capillary bypass channel for conveying a second part of the
10 sample in a first direction from 20 a first region, proximate to the branching

point, to an overflow region, distal to the branching point, the first region
having a capillary dimension in a second direction substantially perpendicular to
the first direction;

e) a second stop junction in the bypass channel, comprising a
15 boundary region that

i) separates the first and overflow regions,

ii) has a second predetermined dimension . in the second
direction that is greater than the capillary dimension, and

20 iii) forms an angle that points toward the 5 first region,

whereby any excess sample that enters the sample inlet will pass through
the second stop junction into the overflow region.
Devices of the present invention provide, in a capillary flow channel of the
device, a stop junction that is angular in the flow direction. Such a stop junction can be
25 designed with readily-controlled breakthrough pressure. Note that in the present

specification and the figures, capillaries are shown bounded by parallel plates. In that
case, the "second direction", which has the capillary dimension, is uniquely determined.
Alternatively, capillaries of the invention could be cylindrical. In that case, the second
direction is radial, in a planar circle, or disk, that is perpendicular to the direction of
30 fluid flow.

BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 depicts the operation of a stop junction in a medical device.
35 Figs. 2-5 depict the flow of a fluid in part of a device of this invention.

SUBSTITUTE SHEET (RULE 26)

WO 01/75433

PCT/USOl/09237

-5-

Fig. 6 is an exploded perspective view of a device of this invention.
Fig. 7 is a plan view of the device of Fig. 6.
Figs. 7A, 7B, and 7C depict sample filling the device of Fig. 6.
Fig. 8 is a plan view of a preferred embodiment of this invention, which includes three
5 measurement areas.

DETAILED DESCRIPTION OF THE INVENTION

When fluid flows through a channel, a discontinuity in channel cross section
can form a "stop junction," which can stop the fluid flow, as described in U.S. Patents

10 4,426,451; 5,230,866; and 5,912,134, incorporated herein by reference. The stop

junction results from surface tension that creates a back pressure that stops 15 the
fluid meniscus from proceeding through the discontinuity. The stop junction is
weakened, and flow thereby enhanced, when the leading edge of the meniscus
encounters the vertex of an acute angle and is then stretched along the arms of the

15 angle. This may be 20 described as the angle "pointing" in a direction opposite to the
direction of fluid flow.

This invention relates to a medical diagnostic device that has a flow channel
with a stop junction. The stop junction is angular in the direction of flow, which 25

permits fluid in the channel to break through, the stop junction when there is a

20 predetermined pressure difference across the stop junction. The advantages of such a
controlled break-through stop junction are apparent from the description that follows.

Fig. 1 depicts part of a medical diagnostic strip 10 that is a multilayer sandwich.
Top layer 12 and bottom layer 14 sandwich intermediate layer 16. A cutout in

25 intermediate layer 16 forms channel 1 8. Lines 20 and 20A 5 are scored into the
bottom surface of layer 12 and form in channel 18 stop junctions 21 and 21 A,
respectively. Thus, sample S, introduced into channel 18 at sample inlet 22, stops when
it reaches stop junction 21 .

Figs. 2 and 3 depict the part of a medical to diagnostic strip of Fig. 1 in which

30 stop junctions 21 and 21 A have been modified by adding serrations 24 and 24A,

respectively. Serration 24 forms an acute angle A that "points" toward sample inlet 22.
Figs. 2 and 3 depict sample S just before and just after it breaks through stop junction
21, respectively. Note that the breakthrough occurs first at the vertex that points
opposite to the direction of fluid flow. The effectiveness of the serration in enhancing

35 flow through a stop junction in a capillary channel depends on the angle and the length.

SUBSTITUTE SHEET (RULE 26)

WO 01/75433 PCT/US01/09237

-6-

of the legs that form the angle. The smaller the angle and the longer the legs, the greater
the effectiveness of the serration. Thus, if the angle is small and the legs long, only a
small hydraulic pressure differential across the scored region will cause the sample to
flow through it. Preferably, angle A is less than about 90° and its axis of symmetry is
5 aligned with the direction of flow in the channel.

Stop junction 21 A has an angle that points toward end 26 of channel 18 that is
opposite inlet 22, and it would have reduced resistance to the flow of sample that
entered end 26. Figs. 4 and depict the flow of sample through channel 18 after it has
broken through stop junction 21. In Fig. 4, the sample is stopped at stop junction 21 A.

10 In Fig. 5, sample has passed through stop junction 21 A at its two ends. The

breakthroughs, occur there, because although the angles at the two ends are greater than
90°, they are smaller than the angle (i.e., the supplement of the angle that points toward
26) at the center of serration 24A. A short time after the sample 10 reaches the position
shown in Fig. 5, the sample will pass through stop junction 21 A across the entire width

15 of channel 18.

Fig. 6 is an exploded perspective view of an embodiment of the present f
invention. The diagnostic device 30 has a top layer 32 and bottom layer 34
sandwiching intermediate layer 36. Elements of the device are formed by the layers,
together with cutouts in them. Depicted in Fig. 6 are sample inlet 38, formed by

20 coaligned holes in intermediate layer 66 and top layer 32; first capillary channel 40, for
conveying sample from sample inlet 38 to branching point 42; and capillary connecting
channel 44, for conveying sample through measurement area 46 to a first stop junction
48. Stop junction 48 is formed by the intersection of the 25 capillary neck, at the end of
measurement area 46, and the coinciding holes 48 A, 48B, and 48C in intermediate

25 layer 36, top layer 32, and bottom layer 34, respectively. Holes 48A, 48B, and 48C are
conveniently punched in a single operation when the layers are together. In a less-
preferred embodiment, only two holes are needed. Thus 48B or 48C could be omitted.
Measurement area 46 preferably contains a reagent 50. Cutout 5 8 . is part of a bladder
that includes the 5 adjoining regions of top layer 32 and bottom layer 34. Capillary

30 bypass channel 52 provides an alternate path from branching point 42 to overflow

region 54. A stop junction 56 in bypass channel 52 impedes flow into overflow region
54. Stop junction 56 is formed by the intersection of capillary bypass channel 52 and
the coinciding holes 56A, 56B, and 56C in intermediate layer 36, top layer 32, and
bottom layer 34, respectively. (Either hole 56B or 56C can be omitted). Note that stop

35 junctions 48 and 56 also require seals 48D, 48E, and 56D, 56E, respectively. -

SUBSTITUTE SHEET (RULE 26)

WO 01/75433

PCT7US01/09237

-7-

Fig. 7 is a top plan view of the device of Fig. 6. The device depicted in Figs. 6
and 7 is particularly well suited for measuring blood-clotting time - "prothrombin time"
or "PT time" - and details regarding such a device appear below. The modifications
needed to adapt the device for other medical diagnostic applications require no more
5 than routine experimentation. In operation, sample is applied to sample port 38 after
bladder 58 has been compressed. Clearly, the region of top layer 32 and/or bottom
layer 34 that adjoins the cutout for bladder 58 must be resilient, to permit bladder 58 to
be compressed. When the bladder is released, suction draws
sample through first capillary channel 40 to branching point 42 and through capillary

10 connecting channel 44 to measurement area 46. In order to ensure that measurement
area 46 can be filled with sample, the volume of bladder 58 is preferably at least about
equal to the combined volume of first channel 40, connecting channel 44, capillary
bypass channel 52, and measurement area 46. 1 the measurement method is optical, and
the measurement area 46 is to be illuminated from below, bottom layer 34 must be

15 transparent where it adjoins measurement area 46.

For a PT test, reagent 50 contains thromboplastin that is free of bulking reagents
normally found in lyophilized 1 0 reagents.

As shown in Figs. 6 and 7, sample is drawn into the device by suction, caused
by decompression of bladder 88. When the sample reaches stop junction 48, sample

20 flow

stops. For PT measurements, it is important to stop the flow of sample as it reaches that
point to permit reproducible "rouleaux formation" - the stacking of red blood cells -
which is an important step in monitoring blood clotting using the present invention.

The function and operation of the bypass channel can be understood by
25 referring to Figs. 7 A, 7B, and 7C which depict a time sequence during which a sample
is drawn into device 30 for the measurement.

Fig. 7A depicts the situation after a user has applied a sample to the strip, while
bladder 58 is compressed. This can be accomplished by applying one or more drops of
blood.

30 Fig. 7B depicts the situation after the bladder is decompressed. The resulting

reduced pressure in the first channel 40 and connecting channel 44 draws the sample
initially into the measurement area 46. When the sample reaches stop junction 48, the
sample encounters a back pressure that causes it to stop and causes additional sample to
be drawn into the bypass channel toward stop junction 56. Note that stop junction 56 is

35 "weaker" than stop junction 48, because it has an angle A that points toward branching

SUBSTITUTE SHEET (RULE 26)

WO 01/75433

PCTYUS01/09237

point 42. (See Figs. 1-5). Thus weak stop junction 56 performs two functions. It first
impedes the flow of sample into overflow region 54, thus permitting measurement area
46 to fill rapidly. Second, it permits any excess sample to flow through it (after
measurement area 46 is full) to relieve any pressure difference remaining on the two
5 sides of stop junction 48. Such a pressure difference could cause sample to "leak"
through stop junction 48, causing 15 movement of sample through the measurement
area, which is undesirable, for the reason discussed earlier.

Fig. 7C depicts the situation when an equilibrium has been established among
the pressures on the sample surfaces - atmospheric pressure on the sample in inlet 38

10 . and the pressure on the free surfaces in overflow region 54 and stop junction 48.

Fig. 8 depicts a preferred embodiment of the present device that includes three
measurement areas. For a PT test, measurement area 146 contains thromboplastin. 25

Preferably, measurement areas 146A and 146B contain controls, more
preferably, the controls described below. Area 146A contains thromboplastin, bovine

15 eluate, and recombinant Factor Vila. The composition is selected to normalize the
clotting time of a blood sample by counteracting the effect of an anticoagulant, such as
warfarin. Measurement area 146B contains thromboplastin and bovine eluate alone, to
partially overcome the effect of an anticoagulent. Thus, three measurements are made
on the strip. PT time of the sample, the measurement of primary interest, is measured

20 on area 146. However, that measurement is validated only when measurements on
areas 146 A and 146B yield results within a predetermined range. If either or both of
these control measurements are outside the range, then a retest is indicated. Extended
stop junction 148 stops flow in all three measurement areas. Stop junction 156, in
bypass channel 152, functions as described above.

25 Additional details on this embodiment of the invention appear in copending

U.S. Patent Application Serial No. 09/333,765, filed on June 15, 1999, and
incorporated herein by reference.

SUBSTITUTE SHEET (RULE 26)

WO 01/75433

PCT/US01/09237

I Claim

1 . A medical diagnostic device for measuring an analyte concentration or property
of a biological fluid; comprising

a) a sample inlet for introducing a sample of the biological fluid
5 into the device;

b) a first capillary channel for conveying the sample from the inlet
to a branching point;

c) a capillary connecting channel for conveying a first part of the
sample from the branching point through a measurement area, in which is

10 measured a physical parameter of the sample that is related to the analyte

concentration or property of the fluid, and to a first stop junction;

d) a capillary bypass channel for conveying a second part of the
sample in a first direction from a first region, proximate to the branching point,
to an overflow region, distal to the branching point, the first region having a

15 capillary dimension in a second direction substantially perpendicular to the first

direction;

e) a second stop junction in the bypass channel, comprising a
boundary region that

i) separates the first and overflow regions,
20 ii) has a second predetennined dimension in the second

direction that is greater than the capillary dimension, and

iii) forms an angle that points toward the first region,
whereby any excess sample that enters the sample inlet will pass through
the second stop junction into the overflow region.

25

2. The device of claim 1, further comprising a suction device, in fluid
communication with the first and second stop junction, for drawing sample from the
sample inlet toward stop junctions.

30 3. The device of claim 2, in which the device comprises a first layer and second
layer, at least one of which has a resilient region over at least a part of its area,
separated by an intermediate layer, and in which

a) cutouts in the layers form, with the layers, the sample inlet, first
channel, connecting channel, measurement area, and bypass channel;
35 b) the suction device comprises a bladder that

SUBSTITUTE SHEET (RULE 26)

WO 01/75433

PCT/US01/09237

-10-

i) is distal from the sample inlet,

ii) comprises at least a part of the resilient region, and

iii) has a volume that is at least about equal to the combined
volume of the first channel, measurement area, connecting channel, and

5 bypass channel, and

c) the first and second stop junctions comprise coinciding holes in
the first, second, and intermediate layers that are sandwiched by a third layer
and fourth layer.

10 4. The device of claim 3 in which at least the first or second layer is substantially
transparent adjoining the measurement area, and the physical parameter that is
measured is optical transmission.

5. The device of claim 3 in which the physical parameter of the sample undergoes
15 a change in the measurement area.

6. The device of claim 5 in which the measurement area contains a composition
that facilitates blood clotting, the biological fluid is whole blood, and the property
being measured is prothrombin time.

20

7. The device of claim 6 in which the composition comprises thromboplastin.

8. The device of claim 6 further comprising at least 20 one additional fluidic path
from the branching point to the bladder, each such alternate path including a

25 corresponding measurement area and stop junction.

9. The device of claim 8 in which a first alternate path is to a measurement area
that overcomes the effect of an anticoagulant and a second alternate path is to a
measurement area that partially overcomes the effect of an anticoagulant

30

10. The device of claim 9 in which the measurement area in the first alternate path
comprises thromboplastin, bovine eluate, and recombinant Factor Vila and the
measurement area in the second alternate path comprises thromboplastin and bovine
eluate.

35

SUBSTITUTE SHEET (RULE 26)

SUBSTITUTE SHEET (RULE 26)

WO 01/75433

PCT7US01/09237

SUBSTITUTE SHEET (RULE 26)

WO 01/75433

PCTYUS01/09237

SUBSTITUTE SHEET (RULE 26)

WO 01/75433

PCT/US01/09237

FIG. 7B FIG. 7C

SUBSTITUTE SHEET (RULE 26)

WO 01/75433

PCTYUS01/09237

FIG. 8

SUBSTITUTE SHEET (RULE 26)